This invention relates to a dental applicator, and, in particular to a disposable applicator for applying a compound, such as a fluoride-containing resin sealant, to the surfaces of teeth or their roots without creating an irritating build-up of the compound in the gingival margin.
Since the discovery of the effects of topical fluoride preparations by Bibby in 1942, much dental research has involved the development of topical fluoride preparations and systems which would enhance the fluoride uptake by tooth enamel. In recent years, researchers have determined that incorporating fluoride into a varnish or sealant prolongs the reaction time of the enamel with the fluoride and increases the fluoride uptake by the enamel. Recently, researchers have incorporated fluoride compounds into light-curable resins to create a fluoride-releasing resin to apply to teeth to increase the exposure of enamel to fluoride. For example, one approach is to incorporate a fluoride-bearing ingredient as a chemical component of a resin which, by ion exchange or hydrolysis, releases fluoride for uptake into the enamel. A slow release of fluoride ions over a long period of time promotes remineralization of dental caries and surrounding enamel. Furthermore, the application of the fluoride-exchanging resin to the intact tooth surface is now known to prevent the development of dental caries.
In addition to treatment of dental caries and enamel, the fluoride-containing resin technology is effective in treating exposed roots and root caries. Root caries disease is on the increase because older persons now retain their natural teeth longer. Often, root caries develop because gingival tissue recedes from the tooth and exposes the root. Exposed roots are hypersensitive to thermal, mechanical, or chemical stimuli resulting in discomfort and pain. Since the root surface is hypersensitive, it deters proper oral hygiene, such as brushing, and often exacerbates caries development. Researchers have found that application of fluoride-containing resins allows for fluoride uptake into the root dentin and seals dentinal tubules and thus prevents caries formation. Research has also shown that the use of a slow-release fluoride-containing resin reduces cervical hypersensitivity of teeth with exposed buccal root surfaces. This treatment modality is particularly useful where, for example, the gingival tissue has receded from the tooth, exposing roots and creating a hypersensitive surface. Exposure to the slow-release fluoride promotes remineralization of the tooth and its root and also acts as a pit and fissure sealant.
One such product, that has shown in vitro deposition of bound fluoride in substantial amounts, is a slow-release light curable resin formulation of Bis-GMA resin (2,2-bis[4(2- hydroxy-3-methacryloloxy-propyl-oxy)-phenyl]-propane) and a boron trifluoride amine complex, containing 2.70% fluoride from which fluoride ions are slowly released by hydrolysis. The product is manufactured under the name "ENDURA-F" by Kerr Manufacturing Company of Santa Ana, Calif.
Dental compounds, such as "ENDURA-F", are typically applied to the tooth by an applicator, such as the applicator 1 shown in FIGS. 1 and 2. The applicator 1 has a handle 3 with a pick end 5. A tuft 7 of absorbent material or filaments is secured to the end of pick section 5. In practice, the application procedure is relatively simple. The dentist or hygienist isolates the surface of tooth T, for example, with cotton rolls. The buccal surface of the tooth and/or root R is acid-etched with an acid solution, for example, a solution of 37% phosphoric acid, such as Concise Enamelbond available from 3M Company of Minneapolis, Minn., for approximately five seconds. The dentist rinses the tooth and root with water and dries them with compressed air and suction. Utilizing the prior art device and method, the dentist dips the point 5 and the tuft 7 of the applicator 1 into a container of sealant (not shown) to saturate the tuft 7. The dentist swabs the tooth T and its root R with the pointed tip 5 and the tuft 7 introducing the sealant S into the gingival margin M. The dentist then exposes the tooth to a curing light, such as a "Command Light" available from Kerr Company of Santa Ana, Calif., and the resin is polymerized and hardened. Generally the sealant stays on for approximately six months before reapplication.
There are some notable problems associated with the above described procedure involving the use of the conventional pick-like applicator, such as the applicator 1. With that type of applicator, the dentist generally introduces the resin material to the tooth and root surfaces below the gingival (gum) line, as seen in FIG. 2. After curing, a fillet or sharp-edged ledge line of hardened resin S forms at or below the gingival margin M, creating an irritant. If the fillet is observed after curing, the dentist can trim the excess resin at the gingival margin to remove the irritant. However, the dentist may miss some hardened resin. Further, resin which has hardened below the gingival line may not be accessible to trimming and may remain as an irritant. The constant irritation of the gum by the line of hardened resin is uncomfortable. The irritation may result in pain and bleeding, or result in an infection.